This invention relates generally to pressure transducers, and more particularly to pressure transducers of the electromagnetic induction type.
A pressure transducer is a device which converts pressure, as detected by the mechanical deflection of a diaphragm, into an electrical output. A typical pressure transducer of the induction type couples the mechanical deflection of the diaphragm to a moveable target which is positioned near a coil. The movement of the target, which is formed of an electrically conductive material or of a magnetic material, causes the inductance of the coil to change. When the coil is connected as the arm of a bridge circuit, the change in inductance of the coil causes a bridge unbalance or output signal which is then used to determine pressure.
A variation of this device places two coils and two targets in a housing with the diaphragm at an end of the housing, as described in U.S. Pat. No. 2,614,244, issued to E. B. Moss et al. Each target is associated with one of the coils. One target is fixed in relation to the other target and each is moveably coupled to the diaphragm. The two coils are connected as adjacent arms of a four arm bridge circuit. While the two coil arrangement is an improvement over the one coil arrangement, this device has two major drawbacks. First, the output of the two coil system is low. Second, temperature compensation is difficult in high temperature environments since only two of the four bridge arms are in the high temperature environment. High temperature environments also limit the target to an electrically conductive material, since magnetic materials become unstable at high temperatures.
It is therefore an object of the present invention to provide a pressure transducer with improved output over large ranges of pressure and temperature.
It is another object of the present invention to provide a pressure transducer suitable for use in high temperature environments.
Additional objects, advantages, and novel features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.